Tonight, I threw together the Critter and Guitari Arduino Pocket Piano Arduino Shield.

Some quick thoughts:

• Critter and Guitari’s instructions aren’t very good. Use Make’s.
  
• Why no sockets, C&G? I ended up soldering the multiplexers in sans sockets, but used one of my own for the DAC chip.
• It’s kind of a pain (for me) to upload new programs – my only “shieldworthy” Arduino board is an NG – and thus I have to hit the reset button to upload a new program. As long as I have a little thin stick with me, I’ll be ok. For anyone just getting on board the Arduino train, you’ll probably be using a Diecimila and won’t have this problem – it autoresets when you upload a program.
• The “FM Synthesizer” program is quite fun. It’s no DX7, but you can edit multiple parameters at once, unlike a DX7…

Now to figure out an enclosure…

Also, does anyone know of any programs for the Pocket Piano other than C&G’s? A quick search didn’t turn up much.